Manufacture of steel sheets



March 28, 1933 A. R. GooDHuE MANUFAGTURE oF STEEL SHEETS Filed Nov. 21, 1951 Patented 28, 1933 l N UNITED STATES PATENT lol-FlcE Anemia: n.. eoonmm. or vmsnonrrr, PENNSYLVANIA, AssreNoa ,fro AMERICAN amr um lrnv PLATE COMPANY, A coRroRa'rroN or NEW :mnsEY IANUFACTURE F STEEL SHEETS Application led November 21, 1931. Serial No. 576,596.

This-invention -relates to the manufacture of high silicon electrical steel sheets, and has for its ob'ect the provision of a novel method of manu acturing such sheets whereby they are cleaned of all scale and have a smooth clean surface, so as to provide an improved space factor over 'such sheets as heretofore manufactured.

I- Ii h silicon electrical steel sheets are used ma electrlcal apparatus, such asl the cores .of

transformers, generators and the poles of.

motors and dynamos, that demand a high magnetic permeability and electrical resist- T ance of eatest eic'iency. In the construction of t ese apparatus the high silicon eleci trical steel sheets are stacked one upon the other, with light insulation between the msheets, and it is important, in order to get the r greatest efficiency from the apparatus, that the sheets' should stack tightly against a separate 'm'sulation' so 4as to eliminate the air pockets in the structure. This tight or close stacking of the sheets is known as the space i factor and it is important, in order to have the :best ossible space factor, that the surfaces of t e sheets be smooth and clean, so as to eliminate any unnecessary spacing or air pockets between the sheets.

I Briefly, this method consistsl in an improved series of pickling and cleaning steps after the sheets` have been' annealed, which steps serve to completely remove all scale and foreign matter om--the surfaces of the sheets. n

The drawing forming part of this specification illustrates diagrammatically the apparatus used in carrying out the several steps of this invention.

D The high silicon steel sheets to be treated in accordance with this invention are generally ""rst normalized, cold rolled and box annealed, although any of the usual steps of manufacture may be used-up to the anneal- 5 ing step. After the sheets are annealed they are mounted in a suitable picklin rack 1 in spaced relation to each other. he spaced relation'of the sheets may be maintained in any manner, such as by the use of separating 0 pins, commonly used for this purpose. After in the construction of those parts of ,No inhibitor is used in the above picking -tank 4 for from two to five minutes.

the sheetsare mounted in the pickling rack they are immersed in 'a pickling solution'of approximately 71/2 per cent. sulfuric acid, which isy maintained at from 170 to 180 degrees Fahrenheit,^ contained in a pickling tank 2 for a period of from four to twelve minutes. K

- The pickling solution in the tank 2 is discarded when the Baume exceeds degrees.

solution. 1

' After the sheets have been suitably pickled inthe solution in the tank 2 the rack of sheets will be removed from the tank 2 and immersed in a clean, cold water bath in a tank 3, Where they may be agitated or otherwise manipulated to thoroughly wash the sheets so as to remove all loose scale and to cool the sheets down to room temperature. The cooling of the sheets at. this point in the process is essential, since the hot sheets should not be immersed in the next solution.

After the sheets have been thoroughly cleaned and cooled the rack l will be removed. from tank 2 and lowered into the tank 4, 75 which contains a 3/4' to2 per cent. nitric acid solution maintained at approximately 70 degrees Fahrenheit. The sheets are allowed to. remain in the nitric acid solution in the This solution serves to soften andloosen substantially all the `oxid and scale remaining onthe surfaces of the plates. It is important that the nitric acidsolution in the tank 4 be maintained in a substantially fresh condition, and the solution, theraefore, :isv discarded after every five or six b tches of plates have been immersed therein.

-The rack of sheets is removed from the '9o tank 4 and is next lowered into the 4tank 5 containing clean, cold water, where it is suitably manipulated to thoroughly wash the y sheets and remove all the oxidfscale and other foreign matter loosenedor softened by the nitric acid. The rack-of sheets is removed from the tank 5 and lowered into the tank 6 containing an alkaline solution such as a solution of soda ash in water, which solution serves to neutralize any acid still re-` 100 :saV

- maining on the plates, so as to prevent fur- 4 ther reaction with the metal.

Therack of sheets is next removed from the tank 6 a'iid the cleaned sheets are removed I -5 'from the rack 1 and -piled u on a table 7,

where they are then fed sing y through the remaining apparatus for the remaining suc-V cessive stepsv ofthe method.l The .sheets Vare singly fed from 'the table 7 continuously through a boshl 8 containing approximatelyA Y a 7 .per cent.A solution of sulfuric acid maintained at approximately 200 degrees Fahrenheit. The sheets pass from the bosh 8 through a pair of wringer rollers 9 which their surfaces andv then pass continuously top and bottom water spraysl 11 which provide a continuou forced spray of clean, hot

faces and serve to feed the sheets forwardly` between a pair of upper and lower air blastl nozzles 13 which provide a continuous forced. blast .of hot air against the sheets to dry pass forwardly klfrom the air nozzles 13 througha heated oven 14 in which they are' baked or heated sufciently to remove all eritrapped moisturefrom the sheets-and provide a finished product which has a scale-free and clean surface.

The 7 per cet. sulfuric-acid solution in the bosh 8 is preferably discarded and anew solution 'supplied to the bosh after approximately 30,000 to-40,000 poundsof sheets have been treated or Ahave passed through the bosh 8.

While I have described certain specific apparatus for carrying out this novelfmeth it will be understood that` IJ do not wish to Ybe limited thereto, since variousA forms of apparatus ma be used forcarrying out my method, an the steps of.the method may be claims without departinggfrom the scopeof my invention.

I claim:

1. The method of producing .scale-free, clean, high silicon electrical steel sheets, which consists in spacing the sheets, after being annealed, maintaining a batch of said sheets in spaced relation, pickling said sheets in a hot sulfuric at:id solution,l washing said 60 pickled sheets-iii clean water to remove loose scale, pickling said Washed sheets in asnitric acid solution washing said sheetsv after said 4 last named pickling step iii clean water, then immersiiig saidsheets in an alkaline bath, V passing said sheets through a sulfuric acid squeeze the major portion of the water fromwater against both top and bottom surfacesv all .water from their surfaces. The sheets.

variedwithin the scope of the appended.y

-sheets after said last named pickling step in clean, cold water, then immersingl said sheets in :aii alkaline bath, passing said sheets l singly through a sulfuric acid solution heatv ed tol approximately the boiling point, wash-v ing said sheets to remove all traces of acid, and then drying said sheets by applying heat.

3. The method of clean, high silicon e ectrical steel sheets Which consists in spacing said sheets, after being annealed, maintaining a batch'of. said sheets in spaced. relation, ickling said batch of sheets, washing said pickled sheets to re i move lloosescale, cooling said sheets to ap-IM proximate y room temperatura-pickling said washed and cooled sheets in a mtric acid solution hafving a temperature of not over degrees Fahrenheit, washing said sheets 1 after said last named pickling step in clean, cold water, then immersing said sheets in an alkaline bath, immersin said sheets in a nsulfuric acidsolution an removing the acid from said sheets and drying said sheets by 3 applying heat. l

4. The method of roducing scale-free, clean., high .silicon e ectrical steel sheets which consists 7in spacing said sheets, after4 'being annealed, maintaining a batch of said sheets in/ spaced relation, pickling said batch 0f sheets for from four to twelve minutes in a 71/2 per cent. sulfuric acid solution at from v to 180 degrees Fahrenheit and below 20v degrees Baume, without an inhibitor, washing said batch of pickled sheets'in clean, cold water to remove loose scale and to cool said sheetsto app ximately room temperature, -picklinjg said atch of .washed sheets in a remove the acid, andthei'ildryfingpsaid sheets 'y 'l by applying heat thereto.r l5. The method of oducingsc'lefree, clean, ,highv'silicon e ectrical `steel which consists in spacing said sheets,"v after being annealed, maintaining a batch ofs'aid -1 producing scale-free, 1

1%1 to 2 per cent. nitric-acid pickling solution, `1

alkaline 1 sheets in spaced'relationrpickling said batch of sheets for from four to twelve minutes in a hot sulfuric acid solution, washing said batch of pickled sheets in clean, cold water to remove the loose scale and to cool the batch of sheets to approximately room tem erature, pickling said batch of washed s eets for from two to five minutes in a 5%: to 2 per cent. nitric acid pickling solution, washing said batch of sheets after said last named pickling step in clean, cold water, then immersing said batch of sheets in an alkaline bath2 separating said batch of sheets and passlng said sheets singly through a hot sulfurie acid solution, removing the acidv and washing said sheets with hot water, and then A drying said sheets.

In testimony whereof, I have hereuntoy set m hand. A

y 1 ARCHIE R. GooDHUE. 

